P11B-2503
Suprathermal Fe+ at Earth
2017 Fall AGU
New Orleans
——————————————————————————*
Discovery of Suprathermal Fe+ in and near
Earth's Magnetosphere
S.P. Christon1, D.C. Hamilton2, J.M.C. Plane3, D.G. Mitchell4,
J. Grebowsky5, W. Spjeldvik6, and S.R. Nylund4
Focused Analysis and Research, Columbia, Maryland, USA,
University of Maryland,
Department of Physics, College Park, Maryland, USA, School of Chemistry, University of
Leeds, Leeds, U.K., 4 Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland,
USA, 5 NASA Goddard Space Flight Center, Greenbelt, Maryland, USA, 6 Weber State
University, Department of Physics, Ogden, Utah, USA
1
2
3
Suprathermal (87-212 keV/e) singly charged iron, Fe+, has been
observed in and near Earth’s equatorial magnetosphere using long-term
(1995-2015) Geotail/STICS ion composition data. Fe+ is rare compared
to dominant suprathermal solar wind and ionospheric origin heavy ions.
Earth’s suprathermal Fe+ appears to be positively associated with both
geomagnetic and solar activity. Three candidate lower-energy sources
are examined for relevance: charge exchange of nominal solar wind
Fe+≥7, solar wind transported inner source pickup Fe+ (likely formed by
solar wind Fe+≥7 interaction with near sun interplanetary dust particles,
IDPs), and/or ionospheric outflow of Fe+ escaped from ion layers near
~100 km altitude. Semi-permanent ionospheric Fe+ layers form there
from the tons of IDPs entering Earth’s atmosphere daily. Fe+ scattered
from these layers is observed up to ~1000 km altitude, likely escaping in
strong ionospheric outflows. Using ~26% of STICS’s magnetospheredominated data at low-to-moderate geomagnetic activity levels, we
demonstrate that during those times solar wind Fe charge exchange
secondaries are not an obvious Fe+ source. Earth flyby and cruise data
from Cassini/CHEMS, a nearly identical instrument, show that inner
source pickup Fe+ is likely not important at suprathermal energies. Our
observations, as others, support the lack of a strong lunar Fe+
component. Therefore, lacking any other candidate sources, it appears
that ionospheric Fe+ constitutes at least an important portion of Earth’s
suprathermal Fe+, comparable to observations at Saturn where
ionospheric origin suprathermal Fe+ has also been observed.
+ at
in and
near
Earth’s magnetosphere 2017 Fall Figure
SuprathermalFe Fe
Earth
AGUS0AB
Christon et al. [2017]
+
New Orleans
——————————————————————————*
Observations
6 5
Fe+1:+6 charge states
1
+
(A)
Fe+
+
solar wind Fe
heavy ions
Mg, Si, S
Ne
O
C
O2+
O++
N
104
log10 counts
M [amu]
16
2
+
SW/IM
Solar Wind/
Interplanetary
Medium
3
Ca ,+40Ar ,+ MgO
CO2 , SiO
64
(A)
4
4
+
O
Geotail/EPIC/STICS MPQ Histogram
N
Number
10 2
10 1
10 0
+
Fe
Earth
1995-060 to 2015-365
SW/IM 87-212 keV/e
10 0
MPQ [amu/e]
date: 20.Oct.2017_14:40:08_EDT
start: 1995-063T18:09:07.200
stop: 2015-365T23:56:29.600
no GTL_Xflw
scale GTL MPQ TO
3
+
MI
1
102
ESM_2015000b9515BcBR*2231SW.mhx.gz
10 3
Counts
P11B-2503
+
Triples
Doubles
N* =
37767
0
Ntot = 37767/37767
100
Start: 1995-063T18:09
1
start
( 1995-063T18:09:07.200 )
Stop:
2015-365T23:56
stop
( 2015-365T23:56:29.600 )
DPPS: DV22:31.S0
SCTR: 1:15
MCP:
10
20
40
70
10 1
mpq-triples only
170227-1115
v0.102.jd
G-Factor_060707
XP,is_LH:
Fe+1:+6 charge states 6 5 4
108.3
(B)
Mg, Si, S
Ne
O
C
Boxes_070803
0.50597
4.0
102
ESM_2015000b9515BcBR*2231SH.mhx.gz
+
O
10 4
date: 20.Oct.2017_14:40:26_EDT
start: 1995-060T00:03:28.700
stop: 2015-364T02:59:43.300
no GTL_Xflw
scale GTL MPQ TO
4
+
1
MI
10 3
Number
1.29
104
O+
N+
Geotail/EPIC/STICS MPQ Histogram
N
+
10 2
Fe
Earth
10 0
0.60891
Fe+
solar wind Fe
heavy ions
4
10 1
-9.86
1
Counts
16
2
log10 counts
64
M [amu]
(B) SHEATH
between
bow shock
and
magnetopause
3
MPQ [amu/e]
N* =
Triples
330913
100
1
Stop:
2015-364T02:59
stop
( 2015-364T02:59:43.300 )
DPPS: DV22:31.S0
SCTR: 1:15
MCP:
10
20
40
70
10 1
mpq-triples only
170227-1115
v0.102.jd
G-Factor_060707
1
2
4
Doubles
0
Ntot = 330913/330913
Start: 1995-060T00:03
start
( 1995-060T00:03:28.700 )
1995-060 to 2015-365
SHEATH 87-212 keV/e
10 0
+
8
16
32
XP,is_LH:
108.3
64
-9.86
0.60891
1.29
Boxes_070803
0.50597
4.0
M/Q [amu/e]
Ions to the left of M/Q ~9 amu/e (except O+2 and some H+ and He+)
are mostly from extra-terrestrial sources. Ions to the right are mostly
terrestrial, except those whose names are lighter at ~38-48 amu/e are
likely of lunar origin, and some O+ and Ne+ (at ~20 amu/e).
+ at
in and
near
Earth’s magnetosphere 2017 Fall Figure
SuprathermalFe Fe
Earth
AGUS0CD
Christon et al. [2017]
+
New Orleans
——————————————————————————*
Observations
16
6 5
4
3
2
1
(C)
Fe+
solar wind Fe
heavy ions
Mg, Si, S
Ne
O
C
105
O+ +
N
log10 counts
64
M [amu]
(C) SPHERE
Day/Night
Plasma Sheet
Ring Current
no Boundary
Layers
Fe+1:+6 charge states
4
+
O
102
Counts
P11B-2503
5
+
1
N
MI
+
Earth
Fe
1995-060 to 2015-365
SPHERE 87-212 keV/e
20
2
70
1
(D)
Fe+
solar wind Fe
heavy ions
Mg, Si, S
Ne
O
C
O+
N+
104
4
+
102
Counts
16
3
40
log10 counts
64
M [amu]
LOBE
~above and
below the
SPHERE
100
1
10
Fe+1:+6 charge states 6 5 4
(D)
+
O
4
+
1
N
MI
+
Earth
Fe
1995-060 to 2015-365
LOBE 87-212 keV/e
1
2
4
10
8
20
16
40
32
+
1
100
70
64
M/Q [amu/e]
Ions to the left of M/Q ~9 amu/e (except O+2 and some H+ and He+)
are mostly from extra-terrestrial sources. Ions to the right are mostly
terrestrial, except for some O+ and Ne+ (at ~20 amu/e). Note that ions
at ~38-48 amu/e, likely of lunar origin in the SW/IM and SHEATH, are
not distinct in the SPHERE, but are likely present in the LOBE.
+ in and near Earth’s
FeSuprathermal
magnetosphere
Fe+ at Earth
2017 Fall AGU
riston et al.P11B-2503
[2017]
New Orleans
——————————————————————————*
Ygse
Ygse
GEOTAIL’S ~9 X 30 RE ORBIT
(GSE COORDINATES)
oneGTLorbit
yGSE
BS
30
Fig
solar wind/
interplanetary medium,
outside bow shock (BS)
MPxxxxxxxx
SW/IM
20
xGSE
plasma sheet,
-10
ring current, no
boundary layers
R
SPHERE
e
0
~9
Ygse
10
-20
-30
3-hr points,
one orbit
SHEATH
between magnetopause (MP)
and bow shock
(BS)
-30
-20
-10
~30 Re
0
10
20
30
Xgse
ure 1. Plasma regimes assigned to Geotail’s near-Earth location in Geocentric Solar E
• Geotail has been in this 9 x 30 Re orbit since early-1995
• plasma regimes (explained above) are color coded
rdinates from early-1995 through 2015 are color coded (see text); 3-hr points along one
• The LOBE (not shown) is located above and below the SPHERE
• Small symbols identify Fe+ observations (open for LOBE observations)
Re orbit are• shown.
The SPHERE, the primary plasma regime inside the magnetopause
Sunward of dashed line at XGSE ~ 20 Re, SW/IM is less affected by Earth
taining the plasma sheet, ring current, and near-Earth locations, excludes the magnetos
ndary layers and the LOBE (not shown, but roughly colocated with and lying abov
ow the SPHERE layer). SHEATH locations are outside the magnetopause and inside th
ck (BS), the earthward boundary of the solar wind/interplanetary medium, SW/IM. The
hed line at XGSE ~ 20 Re is the near-Earth bound of a strict SW/IM selection. Small do
Suprathermal Fe+ at Earth
P11B-2503
statsGS3hSkp9215rgn_1yr?
+
+
N /O = 5.35 x 10xKp
+
-0.956
1.45
Fe = 8.58 x 10 x 10xKp
0
(C)
2
R = 0.59
2
R = 0.65
2
10 2
10
10
N+
N+/O+
3
103
10
1
10 1
10
MI+
0
10 0
10
2
10
102
-1
10 -1
10
F107
10 x Kp
-1
-2
10 -2
10
1
10
101
O+,
N+,
O+,
N+,MI+,
MI+, Fe+
Fe+ <Counts>
<Fe+ Counts>
10-2
10
O+
1044
<N+/O+ Count Ratio>
10
-5
Figure 3CD
statsGS3hSkp9215rgn_1yr?t_c
F10.7,
1010xKp,
x Kp, N+/O+
F10.7,
N+/O+
(A)
2017 Fall AGU
Fe+ in and near Earth's magnetosphere
New Orleans
riston et al. [2017] ——————————————————————————*
Fe+ in and near Earth's magnetosphere
Figure
Christon
et al.3AB
[2017]
Fe+
8
9 10
20
<10 x Kp>
(B)
10
+
0
100
10
1995
-0.984
R = 0.84
+
+
-4
0.676
R = 0.29
+
-4
0.789
Fe = 2.73 x 10 x F10.7
Fe = 1.42 x 10 x F10.7
2000
N+/O+
2005
2
2010
Decimal Year
(D)
statsGS3hN_O,Fe_F107mnSter
N /O = 33.9 x F10.7
0
10
40
30
statsGS3hSkp9215rgn_1yr?t**
-3
2015
Fe+/O+
Fe+/N+
-3
-3
10
10
2
2
R = 0.29
2012.5
N+/O+
N+//O+
2009.0
10
Prolonged
Solar Cycle 23-24
Minimum
-1
10
10
22
1995
1995
10
60
70
80
90 100
150
<F10.7>
-5
Solar Cycle
-1
><
|
2000
2000
-3
23
2005
2005
Year
><
|
2010
2010
24
10-4
10
<Counts>
<N+/O+ Count Ratio>
-2
<Fe+ Counts>
10
Fe+/O+,
Fe+/N+
Fe+/O+,
Fe+/N+
-4
10-3
10
2015
2015
Year
200
Figure 3C,D. Plotted versus time are 1-year moving averages of (C) Geotail/STICS suprathermal ions and
+
+
solar
geomagnetic indices, F10.7 and 10 x Kp, respectively, and (D) ion ratios. N /O , plotted in both
gure 3A,B. Scatterplots of 1-year moving averages, stepped every half-year,
ofand
Geotail/STICS
a well-documented solar cycle variation. Ion data are from inside and outside the
/O+ and Fe+ data versus average (A) 10 x Kp and (B) F10.7. Uncertaintiespanels,
shownexhibits
are standard
+
magnetosphere.
Intervals
or of the mean. (A) 10xKp is plotted, where for example, near Kp = 2 values are 10 x Kp (2-, of long-term contemporary Fe and other ions’ roughly correlated variations are
+
highlighted
by
shaded
boxes
in
(C).
Dark
and
light
shaded boxes at the bottom and dashed lines,
and 2+) = 17, 20, and 23, respectively). In (B), open symbols identify Fe data from the
respectively,
show
approximate maximum and minimum solar activity intervals. Uncertainties shown are
olonged Solar Cycle 23-24 minimum. F10.7-Fe+ solar minimum data start and
end times
shown
the moving
averages’
the mid-points times of the points arrows indicate. Power-law fits are discussed
in the
text. standard error of the mean.
Average Geomagnetic Activity <Kp> and Solar Activity <F10.7> Correlation
• Scatterplots of 1-yr moving averages (stepped every half-year) of Geotail/
STICS ion PHA Counts-per-3-hr and ratios thereof versus average: (A) 10 x
Kp and (B) F10.7. Uncertainties shown are standard error of the mean. In
(B), open symbols tag Fe+ data from the prolonged Solar Cycle 23-24
minimum. F10.7-Fe+ solar minimum (arrow times are mid-points).
• Ion data are from inside and outside the magnetosphere.
• Time displays of 1-yr moving averages of (C) Geotail/STICS ions and solar
xxand geomagnetic indices, F10.7 and 10 x Kp, respectively, and (D) ion ratio.
• Power-law fits (light red shading in C) highlight general correlations.
• Dark (light) shaded boxes indicate solar maximum and solar minimum.
Fe+ In and Near Earth's Magnetosphere
Christon et al. [2017]
Figure 4
Suprathermal Fe+ at Earth
P11B-2503
——————————————————————————*
2017 Fall AGU
stGSc3hSkpRID9515SP*Fe+vsKp
104
~
~
10
New Orleans
SPHERE
O+
MI+
3
10
10
10
102
1
10
10
1011
stGSc3hSkpRID9515SW*Fe+vsKp
SW/IM
~~
Average Counts per
3-hr
Average
Counts per 3-hr
Average Counts per 3-hr
Fe+
O+
MI+
Fe+
0
10
10
1000
-1
10
10-1
10
-1
-3
10
10
10-3
00
0
1
10
10
2
20
20
3
30
30Kp
Kp
4
40
40
5
50
50
~
~~~
-2
10
10
10-2
606-9 70
60
70
Kp
Detailed Geomagnetic Activity <Kp> Correlation
Figure 4. Average count rates (proportional to flux) of suprathermal ions in the SPHERE and
SW/IM
plasma regimesions’
are plotted
versus
the average Kp (see(proportional
text). Uncertainties
shown
Suprathermal
average
Counts-per-3-hours
to flux)
in are
the
standard error of the mean. All species show an increase with Kp in both regimes. The rates in
SPHERE
andthan
SW/IM
regimes
are plotted
versus
Kp-ranges
({0o,0
+},
the sphere
are higher
in theplasma
solar wind.
Short-dash
color lines
connect
to the highest
point
which{1-,1o,1
has a wider
Kp+},…,
range,{5-,5o,5
including+},
6 ≤{6-,6o,…,9o}).
Kp ≤ 9.
+},average
{2-,2o,2
Standard error of the
means are shown. All species show an increase with Kp in both regimes.
Rates in the sphere are higher than in the solar wind. Short-dash color lines
connect to the highest point which has a wider average Kp range, including 6
≤ Kp ≤ 9.
Fe+ in and near
magnetosphere2017 Fall AGU
Suprathermal
Fe+Earth’s
at Earth
Christon
et al. [2017]
P11B-2503
New Orleans
——————————————————————————*
11
<
1
Fe+2 box
35
<
2*
12
<
3*
187
Counts:
BKG:
64
4*
<
<
<
<
72<
Fe Charge State: 8 7 6 5
697
266
72
44
SWFe
1 5
Figure 5
2
(A)
Fe
Si
Mg
100
counts
M [amu]
500
16
S
O
C
10
1
4
Ygse
YgseIN
YgseABBL
1
30
30
Geotail/STICS
~36-212 keV/e
2
37 orbit segments
each ≥ 25 hours
4
8
16
M/Q
[amu/e]
slct#D1d_XYseg_F4B
32
64
Kp9515hist,slct#D 4:06:25 PM 3/5/17
30
37 orbit
segments
(B)
20
(C)
Kp for: all/1e3
FeSP
(a) [68216]
KpFes#C
25
All times (÷1000)
allF4Kp/5
1995.0 - 2016.0
20
Fe+ times not in SW/IM
25
20
(c) [527]
number
00
All times in (A) (÷5)
15
(d) [42]
15
All Fe+ times in (A)
80
-10
-10
10
6
37 orbits
Vsw
4
-20
5
each
≥25 hours
-30
-30
-30
-30
-20
-10
-10
00
10
10
20
Number
8
Number x1000
Ygse
YGSE [Re]
10
10
2
1995-2016
200
400
600
10
40
10
V[km/s]
number of intervals
(b) [224]
5
440 km/s
0
0
00 10 20
30
2 30 40
4 50 660 70 80
8 90 100
30
Kp
Kp
XGSE [Re]
Little to No Solar-Wind-Fe+2 or Lunar-Pickup Si+ During Low MI+ Times
Xgse
• Times
at nominal
Kpofwere
selected
whenion
MI+flow,
ions do
mask
the Fe Mass
range
Figure
5. (A)
At times
lower
molecular
37 not
orbit
segments
longer
than 25 hr (~70%
+ - large black
The >25
hr (~70%
≥36selected
hr) orbit
a measured
of •which
are ≥36
hr) were
to traces
captureend
anywith
prior
solar windFe
flows
with swFe and/or ISPU
+
(white)
dots
represent
panel
A
data
in
the
SPHERE
(LOBE);
red,
all
other Fe
Fe+ that could result in the Fe+ observed in the SPHERE and/or the SHEATH
- the most likel
• After considering various backgrounds (some N2+, noise) - few, if any, atomic 28M+
regimes to observe Fe+2+2:+6. The main criterion used to +choose these intervals was a minima
ions (i.e., (a) SWFe secondaries
or (b) lunar origin Si ) are present in the Fe box
+2 box. Fe+1:+8 and background counts from collection boxe
molecular ion presence in the
Fe
• Little evidence here of Si+ superposed over N2+; lunar data show Si+, but no Fe+
inside the heavy black
boundary (shown by arrow) and vertical gray boundaries separating F
• Too few SWFe+2 ions in the red box to charge exchange into the Fe+1 ions
charge states and background boxes are given above (A). (B) Hourly points (small black dots
identify the orbit segments. Large dots identify measured Fe+ locations, where black (open) dot
Journal of Geophysical
Research: Space Physics
+
Christon et al. [2017]
P11B-2503
10.1002/2017JA024414
Fe in and near Earth’s magnetosphere
Suprathermal
Fe+ at Earth
Figure 6
2017 Fall AGU
New Orleans
——————————————————————————*
N+ +
O
64
solar wind Fe
heavy ions
M [amu]
Mg, Si, S
Ne
16
O
C
C+
4
1
10
50
Counts
1
4
1
3-167 keV/e
4
+
N16
+
M/Q [amu/e]O
8
M [amu]
?C
10
(C) CHEMS at Saturn 3-167 keV/e
+
+
NO
64
64
Ne+
+
30
4
1
MI+
105
10
Counts
1
1
(B) CHEMS Cruise
3-167 keV/e
(D)
4
8
16
32
STICS at Earth 9-212 keV/e
1995-061 to 2015-365
~2.7 - 9.0 AU 2000-001 to 2004-180
Interplanetary Space Includes Jupiter Flyby
2
Fe+
solar wind Fe
heavy ions
Counts
1
H2O+
Mg, Si, S
Ne
16
O
C
O+2
1
S+
S+3 S+2
solar wind Fe
heavy ions
Mg, Si, S
Ne
16
O
C
4
32
MI+
2004-182 to 2015-365
~4 < R ≤ 20 Rs MAGNETOSPHERE
M [amu]
64
2
104
10
1.6 - 0.7 - 1.3 AU 1999-003 to 1999-257
Interplanetary Space Excludes Near Earth Flyby
1
C+
Counts
1
(A) CHEMS Cruise
Fe+
solar wind Fe
heavy ions
Mg, Si, S
Ne
16
O
C
O+2
M [amu]
64
+
+
NO
?S+
~9-30 Re MAGNETOSPHERE
mqFe+@eSP
mqFe+@sSP
2
4
1
64
M/Q [amu/e]
Fe
4
10
100
1000
Counts
mqFe+@eSP
INNER SOURCE PICKUP IONS
(ISPUI) most likely do not
contribute puFe+ to near planet ions at Earth.
100
10
8
16
32
64
M/Q [amu/e]
esmcas_Fe_hists
11:38:05 PM 11/19/16
+1:+6
Fe+1:+6 charge
states:
charge states: 6 5
4
3
2
1
Earth
(E)
Fe Box
Histograms
Saturn
10
11
1
1
2
4
10
20 30
10
M/Qmpq[amu/e]
[amu/e]
50 70
Figure 6. Long-term measurements of suprathermal energy heavy ions measured on Cassini’s cruise to Saturn through interplanetary space in (a) in 1999, 41 days in
the inner heliosphere, including the flyby of Earth, and (b) from 2000 to mid-2004, ~4.5 years in the outer heliosphere, including the flyby of Jupiter in 2001,
+
compared to data in the magnetospheres of (c) Saturn by Cassini, and (d) Earth by Geotail. Fe is present at Earth and Saturn but not in interplanetary space. Dashed
+
arrows in Figures 6a and 6b show the expected location of pickup C at M/Q ~ 12 amu/e. Cassini’s passes by Earth and Jupiter were too brief to detect any extant
+
Fe . High-charge-state solar wind Fe is often present in Earth’s magnetosphere, but little solar wind Fe was detected in Saturn’s magnetosphere. (e) Histograms
+ +
+
compare Fe box data from Saturn (Figure 6b) and Earth (Figure 6c). The M/Q range of likely N , O , and MI spillover backgrounds masking Fe data is shaded.
• Produced by dust ionization at the Sun, puC+ is the principal ISPUI ion
•
+
+
puFe /puC
< 0.005 ± 0.005 [Christon et al., 2017; Gloeckler et al., 2010]
+
CHRISTON
ET AL.
16
• (A)
Cassini/CHEMS
likelySUPRATHERMAL
observesIONOSPHERIC
some FEpuATCEARTH
in the inner solar system
+
• (B) Cassini/CHEMS does not observe puC+ from 2 to 9 AU (~Saturn orbit)
• (C, D) C+ is ionized internally in Saturn’s magnetosphere, but not Earth’s
• (D) No C+ is observed at Earth; suggests no ISPUI enter its magnetosphere
• ∴ No C+ at Earth, requires no puC+ at Earth and no puFe+ at Earth
Suprathermal Fe+ at Earth
P11B-2503
2017 Fall AGU
New Orleans
-60
Moon Orbit
~60 Re
4
10 ≤ LLT < 14 hr
——————————————————————————*
5
DUSK
Ygse
Ygse!moon
Ygsemoon
-40
slct#D1d_XYseg_F4Bmoon&!
30
0
20
3
T
A
I
L
10
Ygse
YGSE [Re]
-20
Heavy Ion
Lunar
‘Wake’
~25 Re
0
-10
20
0
S
U
N
-20
-30
-30
-20
40
-10
0
10
20
30
Xgse
2
1
DAWN
60
-60
-40
-20
0
XGSE [Re]
20
40
60
Earth, Moon and Geotail Orbits: Are Lunar Pickup Ions Observed?
• Lunar pickup ions are most likely detected when the Moon is directly
sunward of Geotail’s ~9 x 30 Re orbits, in the lunar local time (LLT) range: 10 ≤
LLT ≤ 14 hr, i.e., ~60º or ~1/6 of the Moon’s orbit. The Moon most likely has a
tenuous ‘heavy ion wake’, drawn ~25 Re wide here to represent heavy ion
(CO2+ or Fe+) gyroradii in the nominal ~5-9 nT IMF at ~1.AU.
• Dotted traces indicate the orbit segments when a Fe+ was measured in the
SPHERE at moderate geomagnetic/solar activity (~25% of all Fe+ data), for
which white (black) squares show Fe+ measured when the Moon was (not) in
the ~10-14 hr LLT range. Red squares show Fe+ measured at all other times.
• Table 1, a FIRST ATTEMPT using statistical arguments to infer Lunar pickup
ion detection, shows that: In the SW/IM Lunar ions likely contribute to 28M+ and
40*M+, but only possibly contribute to Fe+.
P11B-2503
——————————————————————————*
Suprathermal Fe+ at Earth
2017 Fall AGU
New Orleans
Table 1. T-Statistics for Estimating the Presence of a Suprathermal Lunar Ion Component in Near-Earth Plasma
When the Moon is Sunward of Earth or Not, Using Averagea Ion Species PHA Counts per 3-hr Interval
* +
+
+
28
40*M+
Ion
(number
of
N
O
M
NO+
Fe+
———
3-hr intervals)
T ± uTb
T ± uT
T ± uT
T ± uT
T ± uT
T ± uT
___________________________________________________________________________________________________
Regime
————
ALL DATA
LLT
#
(9205)
2.77 ± 0.01
433008
2.71 ± 0.00
1571058
0.21 ± 0.00
3544
-0.04 ± 0.00
17056
4.26 ± 0.22
457
3.57 ± 0.41
96
-1.10 ± 0.00
6553035
0.77 ± 0.01
3407
-0.14 ± 0.00
15146
(46187)
-1.11 ± 0.00
1843869
-1.01 ± 0.04
1236
-1.64 ± 0.13
257
(3408)
3.28 ± 0.09
1734
2.59 ± 0.04
5729
9.13 ± 0.51
501
5.52 ± 0.52
151
5.58 ± 0.55
160
3.50 ± 0.61
45
(16602)
-1.34 ± 0.02
6445
-0.95 ± 0.01
21980
-6.90 ± 0.41
418
-2.73 ± 0.21
293
-4.22 ± 0.44
133
-1.98 ± 0.29
74
0.65 ± 0.01
13953
-0.21 ± 0.00
65531
0.47 ± 0.00
49400
-0.20 ± 0.00
232562
3.58 ± 0.22
359
0.20 ± 0.02 3.03 ± 0.39
167
83
-0.04 ± 0.00
-1.87 ± 0.21
812
128
1.15 ± 0.31
17
-0.46 ± 0.08
57
2.90 ± 0.01
353269
2.86 ± 0.00
1294685
!LLT
#
SW/IM
LLT
#
!LLT
#
SHEATH
LLT
#
(1584)
!LLT
#
SPHERE
LLT
(8186)
-1.37 ± 0.06
857
0.13 ± 0.00
0.85 ± 0.02
0.53 ± 0.05
1.00 ± 0.21
#
(2065)
2084
2734
160
26
!LLT
-1.18 ± 0.00
-1.17 ± 0.00
-0.03 ± 0.00
-0.21 ± 0.00
-0.11 ± 0.01
-0.41 ± 0.06
#
(10262)
1451315
5174057
10071
11072
712
96
_____________________________________________________________________________________________________________
a: Average obtained over all 3-hr intervals over extended time, spatial range, geomagnetic and solar activity
28M+ may include: N2+, Al+, and Si+. 40*M+ may include: Ca+, 40Ar+, MgO+, CO2+, and SiO+.
LLT (!LLT) denotes times when the Moon is (not) sunward of Earth in the lunar local time range 10 - 14 hr
b: uT, the uncertainty in our two-tailed T-Statistic (+, higher than average; -, lower than average), is from the PHA counts of the sample and
population means used to calculate the T-Statistic. Sample calculations for 28M+ in the SW/IM regime (to 3 significant figures) follow, where,
T = (ms-mp)/√(sEs2 + sEp2), m and sE are the mean and standard error, and s (p) represents the sample (population, the sum of the two samples).
#: the PHA count of the sample mean used to calculate the T-Statistic (leading value: the total number of 3-hr intervals in the regime population)
Color Key:gray: T < 2.58, insignificant-through-just significant correlation; black: 2.58 ≤ T < 3.29, significant correlation;
blue: 3.29 ≤ T < ~4.5, highly significant correlation; red: T ≥ ~4.5, very highly significant correlation
P11B-2503
Suprathermal Fe+ at Earth
——————————————————————————*
2017 Fall AGU
New Orleans
Summary
• Geotail, in a ~9 x 30 Re orbit since early-1995, has observed ~200 keV/e
Fe+ in and near Earth’s magnetosphere
• The Geotail/STICS Fe+ ions observed at Earth are similar to the Fe+ ions
observed by Cassini/CHEMS at Saturn
• Earth’s Fe+ flux appears to increase somewhat with both increased
geomagnetic activity and increased solar activity when viewed
collectively in yearly averages, although neither dependence is
statistically significant
• When specifically ordered with respect to Kp (a geomagnetic activity
index), Fe+ shows a positive correlation with increasing Kp very
similar to that of O+ and MI+ at low-to mid Kp, and in the same sense,
but different from that of O+ and MI+ at highest Kp
• Little to no solar wind origin Fe+ (emitted by the Sun) or inner-source
pickup origin Fe+ (from near-Sun ionized dust) are deduced or inferred
from our measurements
• Some lunar Fe+ might possibly be present in the solar wind, SW/IM,
plasma regime, but: (a) we have not yet sorted out convection effects
in our data, and (b) there is little evidence that any lunar Si+, the
dominant lunar pickup ion, is detected in the magnetosphere when
plentiful Fe+ is measured at low-to-moderate geomagnetic activity in
Earth’s magnetosphere. (We note that no lunar origin Fe+ has ever been
reported in the literature although numerous studies have been
launched/operated/enabled/run/etc. attempting to detect it.) A dedicated,
focused analysis of STICS Fe+ data is required to flush out any possible
lunar connection.